This invention relates to an electromagnetically operated fuel injector valve, and more particular to the fuel injector valve suitable for a so-called single point fuel injection (SPI) system in which fuel injection is carried out by a fuel injector valve or fuel injector valves located at a position of an internal combustion engine.
In connection with an electronically and electromagnetically operated fuel injector valve which is controlled in response to electric pulse signals, there has been known one which is provided with an elongate valve member which is slidable in an elongate valve member guide. However, such fuel injector valve encounters the following problems: The elongate valve member and the guide member require high precision machining in order to prevent fuel leakage at the valve member/valve seat interface. Moreover, because of its elongate shape, the mass of the valve member is unavoidably increased, and this in turn adversely affects its response characteristics by high precision. In this regard, the frequency of practical vibration (opening and closing actions) of the valve member is limited to a level of 200 Hz.
Now, with the SPI system in which fuel injection is carried out only at a position, the fuel distribution to engine cylinders is inferior as compared with a fuel injection system in which a plurality of fuel injector valves are disposed for respective engine cylinders. In fuel supply in so-called on-off manner to an internal combustion engine, it is required to inject fuel at the intake stroke of each engine cylinder. Accordingly, in case of a six cylinder engine, the fuel injection must take place three times per one engine revolution and therefore the frequency in the moving action of the valve member is required to be 300 Hz at the engine speed of 6000 rpm. Similarly, the frequency in the moving action of the valve member is required to be 200 Hz at the engine speed of 6000 rpm in case of a four cylinder engine.
It will thus be appreciated that, such requirements cannot be satisfied by a fuel injector valve of an type having the elongate valve member. Hence, such a fuel injector valve is not suitable for a SPI system.